Hábito alimentar de Urotrygon microphthalmum (Delsman, 1941), e de Rhinobatos percellens (Walbaum, 1792) capturadas na pesca de camarões no nordeste do Brasil

Abstract

The feeding habits and trophic ecology of Urotrygon microphthalmum were investigated through observations of of bottom double rigged otter trawls landings in Pernambuco state, Brazil, between march of 2010 and march of 2012. Also, the feeding habits of guitarfish Rhinobatos percellens, were investigated between July/2010 and March/2011, through stomach content analyses of individuals caught from artisanal fisheries in Caiçara do Norte (Rio Grande do Norte state). This works aims to provide biological data for species conservation purposes, since both are captured as by-catch at artisanal fisheries on each location. U. microphthalmum had a total of 338 stomachs analyzed, from which 79 were discarded from dietary analysis due to emptyness or containing just digested material. Thirty one food items were identified in the diet of U. microphthalmum. The species ingests mainly crustaceans among other invertebrates. The diets between males and females were similar and the ontogenetic shift of diet was not observed. Similarly, the diet of species caught in different sampling sites were alike each other. The species trophic level assumed a value of 3.5, classifying it as a secondary order consumer (mesopredator). The diet of guitarfish showed that teleosts are the main food of this species, followed by dendrobranchiata shrimps and brachyuran crustaceans of genus Callinectes. The graphical method when used for young and adults, showed an ontogenetic shift of diet for R. percellens. The main items consumed by juveniles are shrimps and swimming-crabs, while adults feed mainly on teleosts. The trophic level estimated for R. percellens assumed value of 3.6 (i.e. secondary consumer). By the end of the study, it can be concluded that U. microphthalmum and R. percellens are both mesopredator species within each ecosystem. However, each species adopt different feeding habits and this fact reflects upon the habitat usage between those species.